A trustee is a person or entity designated by a person who creates a trust (grantor, settlor, or trustor) to manage and administer the trust for the benefit of the named beneficiary or beneficiaries. The trustee of a trust created for estate planning purposes is often the grantor, settlor, or trustor who created and funded the trust.

A trust agreement may designate one or more successor trustees who will become the trustee if the previous trustee dies, is unable to continue to serve as trustee, resigns as trustee, or is removed by court order following a lawsuit filed by the beneficiary or beneficiaries of the trust.

A trustee has a fiduciary duty to the beneficiary or beneficiaries of the trust. A fiduciary duty includes the highest duty of care (performance of duties under the terms of the trust agreement) and of loyalty (avoiding conflicts of interest) recognized in law.

In Oklahoma, a trustee is responsible for managing a trust in accordance with the terms set forth by the grantor, who may also serve as the initial trustee. The trust agreement can specify one or more successor trustees to take over if the original trustee can no longer fulfill their duties due to death, incapacity, resignation, or removal by a court. Trustees in Oklahoma are bound by a fidarious duty, which is the highest standard of care in legal terms. This duty requires trustees to act in the best interests of the beneficiaries, adhere strictly to the trust's terms, and avoid any conflicts of interest. Failure to meet these obligations can lead to legal consequences, including potential lawsuits from beneficiaries. Oklahoma trust law is governed by both state statutes and relevant federal laws, which outline the framework for the creation, administration, and termination of trusts, as well as the duties and powers of trustees.